1. Field of the Invention
The present invention relates to a vessel drier which heat treats a fluid having a solid material suspended therein to form a powdery material.
2. Description of the Related Art
Powdered materials may be manufactured by heat treating (e.g., drying or pre-sintering) a fluid containing a solid material therein. By way of example, a fluid suspension containing a ceramic component (i.e., a ceramic slurry of a ceramic component and fluid) may be subjected to a heat treatment process using, for example, a vessel drier.
A conventional vessel has three main components: a cylindrical container, a plurality of ceramic balls located in the container and a heater which provides heat to the container.
The heater is provided outside the cylindrical container and heats both the cylindrical container and the ceramic balls located therein. The walls and the ceramic balls apply heat to the ceramic slurry located in the cylindrical container thereby causing vaporization of the fluid from the ceramic slurry. As a result of this vaporization process, a residue of the ceramic component will be formed on the surfaces of the balls and on the walls of the cylindrical container.
The container is driven for rotation about its central axis so as to cause the ceramic balls to continually rub against one another and act much like a mortar and pestle to crush the residue of ceramic material formed on the balls. This yields a powdered ceramic material which is evacuated though an outlet connected to the cylindrical container.
The convention vessel drier has several drawbacks relating to the efficiency at which heat is applied to the cylindrical container. The ceramic powder forming process is a continuous process. New slurry is continually (or at least periodically) added to the container and the resultant powdered ceramic material is continually (or at least periodically) removed from the container. If the amount of the ceramic slurry supplied to the cylindrical container is too great, insufficient heat will be supplied to the ceramic slurry and efficient processing will not take place. The amount of ceramic slurry which can be processed through the vessel dryer is a direct function of the heat transfer between the cylindrical container and a heater. Because the heat transfer between the cylindrical container and a heater of a conventional vessel drier is relatively low, it is not possible to increase the throughput of the heating process to desired levels.
One possible solution to this problem is to provide a larger heater. However, this is not an efficient solution to the problem because the enthalpy per a unit area (the total amount of heat per unit area) which the cylindrical container receives does not increase proportionally to the increase in the size of the heater. Alternatively, a larger heater may be employed and the diameter of the cylindrical container may be increased. However, this results in an undesirable increase in the size of the vessel drier. The effective production yield of the process can also be increased by utilizing a more powerful heater. However, this makes it necessary to provide a vessel drier which uses more refractory material to withstand the additional heat output of the heater.
In view of the forgoing, there is a need to provide a vessel drier which will maintain a high production yield even though the amount of a raw material per a unit time treated by the vessel drier increases.